Dear EarthTalk: Is it true that biologists want to bring African and Asian wildlife to roam free in North America to help restore natural ecological balances here? If so, what are the implications for biodiversity and our environment?

—Naturegirl, Victorville, CA

A group of biologists and environmentalists is advocating just such a plan to help save wild animals from extinction and restore the ecological vitality of North America’s wildlands to a state that existed before humans set foot on the continent some 13,000 years ago. The concept—whereby large mammals are reintroduced across the continent to fill ecological gaps abandoned eons ago—was first posited publicly two decades ago by bio-geographer Paul Martin of the University of Arizona.

In arguing for the introduction of lions, elephants, camels and other large mammals from around the world to North America, Martin cites the important role that so-called "megafauna" play in maintaining overall ecosystem integrity, including keeping predator/prey populations in balance and invasive species in check. Some conservationists like the idea because hosting such large mammals would require a large amount of preserved, natural open space for habitat. Others see it as a terrible idea, citing human safety issues and the difficulty such exotic animals might have adapting to such different landscapes and ecosystems.

Building on Martin’s ideas, a group of conservationists came together in 2004 to form the New Mexico-based Rewilding Institute. Members of the group co-authored a 2005 commentary in the scientific journal Nature, in which they suggested starting with a series of controlled experiments on fenced private land, as was previously done with condors and bison and led to population rebounds. Some of the first species suggested for North American introduction include giant tortoises, wild horses, camels and elephants. If such experiments pan out, cheetahs and lions could be next.

The group also wants to restore native species such as mountain lions and wolves, both of which roamed North America in large numbers before European settlers first arrived in the 1600s. The group argues that the U.S. Fish and Wildlife Service has approached recovery of these animals "in a haphazard and minimalist way."

"Obviously, gaining public acceptance is going to be a huge issue, especially when you talk about reintroducing predators," says Josh Donlan, Cornell biologist and lead author on the Nature article. "There are going to have to be some major attitude shifts [including] realizing predation is a natural role, and that people are going to have to take precautions."

Donlan adds that "rewilding" could be a win-win situation as far as people and wildlife are concerned. Portions of the Great Plains, for instance, could see an increase in tourism dollars as people flock there to see the wildlife, while the animals themselves—many of which are seriously endangered in their native lands—can take advantage of increased habitat and a decreased threat of extinction.

Dear EarthTalk: Is removing the salt from ocean water (desalination) a feasible fix for the world’s shortage of fresh water?

—Nora Jones, Sydney, New South Wales, Australia

Fresh water scarcity is already posing major problems for more than a billion people around the world, mostly in arid developing countries. The World Health Organization predicts that by mid-century, four billion of us—nearly two-thirds of the world’s present population—will face severe fresh water shortages.

With human population expected to balloon another 50 percent by 2050, resource managers are increasingly looking to alternative scenarios for quenching the world’s growing thirst. Desalination—a process whereby highly pressurized ocean water is pushed through tiny membrane filters and distilled into drinking water—is being held forth by some as one of the most promising solutions to the problem. But critics point out it doesn’t come without its economic and environmental costs.

According to the non-profit Food & Water Watch, desalinated ocean water is the most expensive form of fresh water out there, given the infrastructure costs of collecting, distilling and distributing it. The group reports that, in the U.S., desalinated water costs at least five times as much to harvest as other sources of fresh water. Similar high costs are a big hurdle to desalination efforts in poor countries as well, where limited funds are already stretched too thin.

On the environmental front, widespread desalination could take a heavy toll on ocean biodiversity. "Ocean water is filled with living creatures, and most of them are lost in the process of desalination," says Sylvia Earle, one of the world’s foremost marine biologists and a National Geographic Explorer-in-Residence. "Most are microbial, but intake pipes to desalination plants also take up the larvae of a cross section of life in the sea, as well as some fairly large organismspart of the hidden cost of doing business," she says.

Earle also points out that the very salty residue left over from desalination must be disposed of properly, not just dumped back into the sea. Food & Water Watch concurs, warning that coastal areas already battered by urban and agricultural run-off can ill afford to absorb tons of concentrated saltwater sludge.

Food & Water Watch advocates instead for better fresh water management practices. "Ocean desalination hides the growing water supply problem instead of focusing on water management and lowering water usage," the group reports, citing a recent study which found that California can meet its water needs for the next 30 years by implementing cost-effective urban water conservation. Desalination is "an expensive, speculative supply option that will drain resources away from more practical solutions," the group says.

Despite such arguments, the practice is becoming more common. Ted Levin of the Natural Resources Defense Council says that more than 12,000 desalination plants already supply fresh water in 120 nations, mostly in the Middle East and Caribbean. And analysts expect the worldwide market for desalinated water to grow significantly over the coming decades. Environmental advocates may just have to settle for pushing to "green" the practice as much as possible in lieu of eliminating it altogether.

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